- Introduction
Introduction
Introduction Practical work is an important component of IB chemistry. Approximately 25% of the total teaching time should be devoted to practical work and it makes up 24% of the final assessment mark under the heading 'Internal Assessment' with the external examinations providing the remaining 76%. Much of the practical work will involve experiments in a school laboratory, however 'internal assessment' can be intepreted quite liberally. For example, a well-planned visit (as opposed to a 'tourist visit') to a university research laboratory or industrial site such as a power station or - Devising a programme
Devising a programme
Introduction Your job as an IB chemistry teacher is to devise a practical programme for 40h at Standard Level and 60h at Higher Level which will achieve all the aims for good practical work listed on the Main IA page. It is unlikely that any one single experiment will address all the aims but over the two year period it is perfectly possible to address each of the aims several times through a variety of well designed experiments. It is not an actual requirement but it is good practice to try to - Individual practicals
Individual practicals
Introduction I am including details for many practicals that cover the core (SL and HL) and also some for HL students only that cover the AHL. Some of these can be used to assess Data Collection and Processing (DCP) and Conclusion and Evaluation (CE) but they cannot be used to assess Design (D) as far too much information is given. (Ideas you can use for Design practicals are on a separate page and there is also a separate page for covering ICT in practical work). Whether you make up your own- Practicals for SL & HL
Practicals for SL & HL
Introduction Since SL and HL students are assessed in exactly the same way, i.e. both the criteria and the standards are identical then many practicals are ideal for both levels. This can only be true of course when the theory behind the practical is on the core or the non-extension part of an option. However in some cases, even if the material does involve content from the AHL or option extension material, then it is possible to give some of the relevant information to standard level students so they can- Common chemical reactions
Common chemical reactions
Background I usually start teaching the course with the first part of Topic 2. Atomic structure. Once students know what an atom is I start Topic 1. Quantitative chemistry. If your students have come up through the lower classes in your school they will probably know some basic chemical reactions. Mine come from all over the world with very different backgrounds and with varying knowledge and ability in English. To make sense of quantitative chemistry they need practical knowledge of some basic chemical reactions such as acids reacting with metals, metal oxides - Formula of magnesium oxide
Formula of magnesium oxide
Determining the empirical formula of magnesium oxide Why do the experiment? Many students will have done this experiment before they started the Diploma programme so some teachers are surprised I include it. It is very simple (so there is no separate worksheet) but I find it worthwhile for two reasons. The first is to show that using simple materials can sometimes be better. Traditionally a porcelain crucible is used but I used to find that these often cracked in the heat and were expensive to replace. In addition it was - Acid-base titrations
Acid-base titrations
A traditional acid-base titration Information Before giving this experiment I usually get the students to do a simple acid base titration to introduce them to the correct technique of titration. The experiment is usually to determine the concentration of a solution of sodium hydroxide (about 0.1 mol dm-3) using 0.100 mol dm-3 hydrochloric acid. Students learn about the importance of rinsing out the equipment etc. beforehand and obtaining precise and accurate results. I also introduce the ideas of uncertainty and how they can use the uncertainty written on the apparatus to work out - A green acid-base practical
A green acid-base practical
Background In 2008 a Living Planet report calculated that humans are using 30% more resources than the Earth can replenish each year. As more and more people from the developing world aspire to the same quality of life as those from the developed world the rate of depletion of resources will increase even more. In IB chemistry we are encouraged to bring 'Aim 8' into our teaching. 'Aim 8' involves raising awareness of the moral, social, ethical, economic and environmental implications of using science and technology. I have developed an environmentally friendly practical that mimics the - Analysis of aspirin tablets
Analysis of aspirin tablets
Information It is an interesting fact that if you buy generic aspirin tablets they are very much cheaper than packets of branded aspirin. The analysis shows that they all usually contain the same amount of aspirin (usually 300 mg per tablet) but the branded tablets contain other ingredients so contain less aspirin in terms of percentage by mass. This practical enables students to determine the percentage of aspirin in various brands of locally available aspirin tablets. They can then work out the cost per gram of aspirin. For best results - CaCO3 in egg shells
CaCO3 in egg shells
A versatile 'back-titration' This practical can be adapted to determine the amount of calcium carbonate in a variety of different substances ranging from eggs shells to the shells of sea creatures, such as crabs, or in natural or artificial stone such as marble, limestone cliffs or lime mortar from old buildings. The basic reaction is simply: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l) It is not practical to measure the exact amount of acid required for a known mass of the sample as it is difficult to - Period 3
Period 3
Introduction Topic 3 requires all students to cover the physical and chemical properties of the elements in Period 3 (Na-Ar). They also cover the changes in nature of the oxides from ionic to covalent and from basic to acidic. Higher Level students (Topic 13) need to explain the physical states and electrical conductivity of both the oxides and the chlorides. They also need to be able to describe the reactions of the chlorides with water. For this reason I have enclosed two different worksheets, one for SL students and one - Chlorine in swimming pools
Chlorine in swimming pools
A simple redox 'titration' Introduction Chlorine is an oxidizing agent and is added to swimming pool water in order to disinfect it. The problem is that there needs to be enough chlorine present to disinfect the water but not too much to cause problems to users. This means that the water needs regular testing. This can be achieved easily using a standard redox titration. Excess potassium iodide is added to a sample of the water. The free chlorine in the pool water oxidizes iodide ions to iodine and the amount of iodine formed can be determined by titration - Boiling points of mixtures
Boiling points of mixtures
A practical on intermolecular forces of attraction This is an excellent practical and well worth doing. It introduces your students to setting up and using reflux apparatus. They have to overcome the practical problem of reading the thermometer through Quickfit apparatus (the mark always seems to be where the joints are). They have to think carefully about how to plot relevant graphs. They can check how accurate their work is by arriving at what should be the same boiling point for the 50:50 mixture by two different ways and by - Enthalpy changes
Enthalpy changes
Introduction This is an excellent practical and well worth doing for several different reasons. It is divided into two parts – in a sense two separate experiments. The first determines directly the enthalpy change for the redox reaction between zinc metal and Cu2+(aq) ions. Because the reaction is not instantaneous students are introduced to the idea of extrapolation of a graph to determine what the temperature rise would have been if no heat had been lost to the surroundings. It is also a good experiment to introduce them to the - Reaction rates
Reaction rates
Introduction Assessment statement 6.1 contains the definition of rate of reaction and asks students to be able to suggest practical ways in which the rate of a reaction can be determined. There are many different methods that can be used in a school laboratory. This practical introduces two methods and as they are both measuring the amount of gas produced over time during the same reaction, one by mass and one by volume, the rates calculated by the two methods can be compared as they should be the same. This - Rate-dependent factors
Rate-dependent factors
Introduction This is one of the classic experiments and you can find many examples giving details of it online. I think it is worth doing as it is tried and tested and gives students a good understand both of what is meant by reaction rate and how increasing either the concentration or the temperature increases the rate of reaction. The experiment relies on the fact that when thiosulfate ions react with acid a precipitate of sulfur is formed. S2O32-(aq) + 2H+(aq) → H2O(l) + SO2 (g) + S(s) This reaction is - Le Chatelier's principle
Le Chatelier's principle
Introduction Using a colour change is one of the best ways to demonstrate chemical equilibrium and Le Chatelier's principle. In fact students will already have met a simple example when they used an acid-base indicator during the titration of an acid with a base although they probably will not have made the connection. I usually demonstrate chemical equilibrium by using a beaker of copper(II) sulfate solution placed on an old overhead projector. I add concentrated ammonia to give the deep blue ammonia complex and then add concentrated ammonia solution. It - Group 7
Group 7
Introduction The chemical and physical properties of the halogens appear under Topic 3.2 on the core. Although the physical properties such as atomic and ionic radii are often covered with the remainder of topic 3 it can make sense to leave the study of their chemical properties until students have covered oxidation and reduction. If they do not understand the concept of redox then much of the chemistry of the halogens will make little sense. Although this practical does not fit the requirements of the assessment criteria it is still - Redox titration with KMnO4
Redox titration with KMnO4
Introduction This is a good experiment to introduce students to the technique of redox titrations. They may already have met a simple form of this (when they used dropping pipettes for the amount of chlorine in swimming pool water) but this practical uses traditional burettes, pipettes and volumetric flasks. A standard solution of acidified manganate(VII) ions is used to determine the percentage by mass of Fe2+ in a sample of iron(II) ammonium sulfate. Iron(II) ammonium sulfate is used in preference to iron(II) sulfate as it is less susceptible to oxidation - Electrolytic cells
Electrolytic cells
Introduction and teacher's notes Electrolysis lends itself to some good practical work. Unfortunately there is little on the syllabus for Standard Level students to do practically. Topic 9.5 requires students to be able to state what happens at each electrode and to describe how current is conducted but the examples are limited to the electrolysis of a molten salt. The Additional Higher Level Material takes this further in 19.2 where electrolysis in aqueous solution is included as is the use of electrolysis for electroplating. Even for the AHL quantitative problems involving Faraday’s - Electrochemical cells
Electrochemical cells
Introduction and teacher's notes There is actually very little on the core part of the syllabus about voltaic cells under Assessment Statement 9.4. All that Standard Level students really need to know is how two half-cells (Mg, Zn, Fe and Cu in solutions of their own ions) can be connected by a salt bridge to produce electricity and draw a diagram to show it (see above). They also need to be able to state that oxidation occurs at the negative electrode (anode) and reduction occurs at the positive electrode - Titrations with a pH meter
Titrations with a pH meter
Introduction and teacher's notes Titration curves strictly fall under the AHL heading 18.4 Acid-base titrations. However Standard Level students need to understand about strong and weak acids and bases, (8.3) and The pH scale (8.4). From Assessment Statement 1.5.2 they also need to be able to calculate the concentration of an acid or base by titration with a standard solution of a base or acid. This practical will give students good experience of using a pH meter. It can also be used to fulfil some of the ICT requirements as - Organic functional groups
Organic functional groups
Information and teacher's notes This is very much a practical introduction to organic chemistry. The aim is to familiarise students with some basic organic compounds and to get them to relate physical and chemical properties to particular functional groups. Almost all of the functional groups are on the core in Topic 10: Organic chemistry and much of this practical relates to Assessment Statements 10.1.13, 10.3.2 and 10.4. There is also a small amount that is on the AHL as benzene, methylbenzene and amines are also included. You can either leave - Hydrolysis of halogenoalkanes
Hydrolysis of halogenoalkanes
Introduction and teacher's notes The study of the nucleophilic substitution reactions of halogenoalkanes cuts right across the Core and the Additional Higher Level material on the syllabus. In Assessment Statement 10.5 Standard Level students need to be able to describe with equations the substitution reactions of halogenoalkanes with sodium hydroxide and it states in the teacher’s note that simulations are available for this. The Assessment statement then goes on to state that SL students must be able to explain these substitution reactions in terms of SN1 and SN2 mechanisms. This means
- Common chemical reactions
- Practicals for HL only
Practicals for HL only
Introduction It may seem a little strange that there are many more practicals listed under SL/HL than there are just for HL. It is good practice to try to include at least one practical on every topic so in theory there should be at least nine listed for HL. However many of those given on the SL/HL pages also contain much HL content. For example Period 3 has a separate student worksheet which also includes the reactions of the chlorides of Period 3 elements and both Electrolytic cells and Electrochemical- Determining pKa for a weak acid
Determining pKa for a weak acid
Teacher's notes This practical is highly suitable for assessment for Data collection and processing (DCP) and for Conclusion and evaluation (CE). It can only be given to Higher Level students as they need to understand about pKa values, pH titration curves and buffer solutions all of which are covered in Topic 18. If you are going to assess it then they should not previously have done the SL/HL experiment on titrations with a pH meter. Essentially the student needs to perform a simple strong acid-strong base titration initially to determine - Percentage of Cu in brass
Percentage of Cu in brass
Background Brass objects have been found dating back as far as 5000 BCE. Brass has many different uses, for example, musical instruments, utility objects such as door handles, coinage and as a decorative substitute for gold. Brass is an alloy of copper and zinc, however the exact composition can vary. Most types of brass contain about 60-70% copper and consequently 30-40% zinc but they may also contain small amounts of other elements such as lead and tin. Interestingly, one of the reasons why brass is used for door handles (in - Redox reactions of vanadium
Redox reactions of vanadium
Introduction This experiment addresses two different areas of the Additional Higher Level (AHL) material. Topic 13.2 is concerned with the chemistry of the first-row transition elements and topic 19.1 covers standard electrode potentials. The electronic configuration of vanadium is clearly on the syllabus but although students are expected to be able to work out the oxidation number of vanadium in compounds such as NH4VO3, VSO4 and V2O5 they do not need to learn any of the specific chemistry of the compounds of vanadium. This experiment uses the characteristic colours of compounds - Determining a Kc value
Determining a Kc value
Background Equilibrium is an important topic in chemistry and one that needs to be understood by students. This particular practical looks at an esterification reaction so reinforces chemistry that is also covered on other parts of the syllabus (e.g. 20.4.1 and D.3.3). It can be difficult in a school laboratory to measure the value of Kc as attempts to determine the concentrations of reactants and products can often disturb the position of equilibrium considerably. Because the rate at which ethanoic acid and ethanol react is quite slow (equilibrium at room - Determining Ea for a reaction
Determining Ea for a reaction
Background This Higher Level practical builds on one of the classic experiments normally used at a pre-IB Diploma level (e.g. GCSE) to show the factors affecting the rate of a chemical reaction. This experiment is variously known as ‘the cross on a tile’ or the disappearing cross’ reaction and involves the reaction between sodium thiosulfate and hydrochloric acid. S2O32- (aq) + 2H+(aq) → SO2 (g) + S(s) + H2O (l) At GCSE the normal procedure is the look first at the effect of concentration by altering the concentration of - Iodination of propanone
Iodination of propanone
Background and theory This practical contains a lot of good Chemistry. Students will determine a rate equation for a known chemical reaction and then use it to suggest a mechanism for the reaction. Rate equations are specifically mentioned under topic 16.1 and reaction mechanisms under topic 16.2 so this is very much a Higher Level only practical on kinetics. A substitution reaction occurs between propanone and iodine in the presence of an acid catalyst according to the equation: H+ CH3COCH3 + I2 → CH3COCH2I + H+ + I- The
- Determining pKa for a weak acid
- Practicals for options
Practicals for options
Information and rationale Unlike the previous programme there is no actual requirement stated in the current programme that practical work must be performed for each of the two options taken. However a good teacher will want to include some relevant practical work on the options. What I have decided to do is give two examples of practicals that could be used for each of the seven options – one at SL (or HL) and one for HL only. The HL only practical covers option extension material. Some of the options- A: Structural determination
A: Structural determination
Introduction and teacher's notes This is a neat experiment which was first designed by my colleague Dr John Devonshire. He originally developed it when MS, IR and 1H NMR formed part of the Additional Higher Level (AHL) syllabus for the two previous programmes which were first examined in 1998 and 2003 respectively. Now it can be used for Option A at both Standard Level and Higher Level. The basic experiment is the hydrolysis of an ester using sodium hydroxide. Students are provided with a pure sample of either methyl salicylate - B: Hydrolysis of starch
B: Hydrolysis of starch
Introduction and teacher's notes The structural properties of starch and cellulose form part of assessment statement B.3.5. This is a relatively simple practical, suitable for both Standard and Higher Level students, but it gives some good chemistry to explain. It involves the structure and hydrolysis of starch and the redox reactions associated with the test for reducing sugars. Many chemists may be more familiar with Fehling’s solution rather than Benedict’s solution but both involve the reduction of blue Cu2+(aq) ions to form a red precipitate of copper(1) oxide, Cu2O(s). Benedict’s - B: Vitamin C determination
B: Vitamin C determination
Determination of vitamin C in a supplement Introduction Vitamin C is one of the vitamins listed in B5: Micronutrients and macronutrients. You will need to discuss its structure and explain why it is water-soluble as well as discuss the causes and effects of a lack of vitamin C in the diet. The picture taken from Man-of-War by Stephen Biesty (Dorling-Kindersley, NY, 1993) graphically shows the effects of scurvy on the gums and teeth! The recommended daily allowance is about 60-70 mg and this can be obtained easily by eating fresh - D: Preparation of aspirin
D: Preparation of aspirin
Introduction and teacher's notes This experiment could actually appear under several headings. I've placed it here under Option D: Medicines and Drugs because analgesics are covered under Assessment Statement D3 and students enjoy making a drug that is on the syllabus (and legal to make in a school laboratory!). It could be given to students who are not studying Medicines and Drugs as an option because it is a good example of recrystallisation. It also addresses Assessment Statement G.9.1 for those Higher Level students who are studying Option G: Further - G: Preparation of cyclohexene
G: Preparation of cyclohexene
Introduction and teacher's notes Topic G3 on the Further Organic Option covers elimination reactions and specifically mentions the dehydration of alcohols with phosphoric acid to form alkenes. This practical exactly illustrates this and by doing the experiment students will gain exposure to three good manipulative skills – reflux, distillation and use of a drying agent. The starting material is cyclohexanol rather than ethanol as it is easier to deal with a liquid product rather than gaseous ethene. Concentrated phosphoric acid rather than concentrated sulfuric acid is used as it does - G: Nitration of nitrobenzene
G: Nitration of nitrobenzene
Introduction and teacher's notes This practical is really for Higher Level students as it is an example of an electrophilic substitution reaction and covers materials listed under Assessment Statement G10 for the Further Organic Chemistry Option. The syllabus actually mentions the nitration of benzene to give nitrobenzene as an example of electrophilic substitution. This cannot be done practically in the laboratory as the use of benzene is banned in schools due to its potential carcinogenic nature. The syllabus also includes under Assessment Statement G 10.4 the explanation as to how
- A: Structural determination
- Other ideas
Other ideas
Details of individual experiments on the Internet In addition to the many experiments I have given in full detail (all of which are especially tailored to meet the Internal Assessment criteria) details of many other individual experiments can be found by searching on the Internet. I have given just a selection below. Remember that they are all written by someone who deserves the credit. What you can do is adapt them yourself to meet the IA criteria if necessary. I have tried to include experiments that are different to those
- Practicals for SL & HL
- Design practicals
Design practicals
Background In order to fulfil the Internal Assessment criteria your students will need to do at least two Design practicals. In reality this means doing about four so that they can learn from their mistakes and have a good chance of achieving high marks for at least two of them. Design practicals are totally different to all the practicals listed under Details of individual practicals as no instructions can be given to the students. Essentially all you do is give them an open-ended problem to investigate. The subject guide gives- Aspect of electrochemical cells
Aspect of electrochemical cells
Design problem The information you give to students is simply, “Investigate an aspect of electrochemical cells”. Teacher’s notes The investigation is highly suitable for both SL and HL. It is obviously sensible to give them this practical excercise after they have studied Assessment Statement 9.4 voltaic cells (and AS 19.1 if they are Higher Level students). There are many obvious variables. These include: The potential difference of the cell The nature of the metal in each half cell (assuming simple cells are used) The oxidation state of the metal - Aspect of enthalpy change
Aspect of enthalpy change
Design problem The information you give to students is simply, “Investigate the effect of one factor on the experimentally determined enthalpy of a reaction”. Teacher's notes This is a sensible problem to give as enthalpy experiments are relatively easy to carry out and you are likely to have already given some good practicals on enthalpy changes as you were covering Topic 5 of the Core (and Topic 15 for Higher Level students). It is usually quite difficult for the student to control heat loss to the surroundings - Aspect of homologous series
Aspect of homologous series
Design problem The information you give to students is simply, “Investigate an aspect of a homologous series”. Teacher's notes This is an interesting exercise to give students as it has enormous scope for both Standard level and Higher Level students. In fact because of the potential changes in polarity of certain molecules as the hydrocarbon chain length increases it could encompass many of the other suggestions for Design experiments given on the introductory page for Design experiments, e.g. Investigate the effect of one factor on the viscosity of a liquid. - Aspect of rate of reaction
Aspect of rate of reaction
Design problem The information you give to students is simply, “Investigate (quantitatively) one factor that affects the rate of a chosen reaction. Teacher's notes Probably this is the most popular of all Design problems to give to students as it can easily be done at both Standard Level and Higher Level. It should also result in enough data collected by the student for you to be able to assess Data collection and processing and Conclusion and evaluation as well as Design. It would be normal to give it to
- Aspect of electrochemical cells
- ICT
ICT
Introduction Aim 7 in the subject guide states: “develop and apply the students’ information and communication technology skills in the study of science”. ICT should be an integral part of your students’ whole learning experience in Chemistry. Although it does not have to be formally assessed, you are now required to address five different areas of ICT at least once during the 40h or 60h spent on the internally assessed part of the programme. The five areas are listed on form 4PSOW and you will need to state when and- Data logging
Data logging
What is a data logger? A data logger is essentially a piece of equipment that records electronic signals at pre-set intervals over a period of time. Data loggers are being increasingly used in society as a whole, for example, to monitor traffic, to monitor wind speed, temperature and humidity in unattended weather stations and in environmental monitoring units to measure pollution levels. For experiments in a school laboratory a data logger can be seen as a device to measure the independent variable electronically and record and store the data. There - Graph plotting software
Graph plotting software
Rationale The IB stipulates that students must use graph plotting software at least once during their practical course but it does not have to be for an assessed practical. Maybe I am a little old fashioned but I still like to get students to plot at least one graph by hand so that they fully understand how to use scales correctly. This is because I see from marking Paper 2 data response questions that a surprising number of students worldwide still cannot read a graph correctly even at the end - Spreadsheets
Spreadsheets
Introduction Spreadsheets in their current form have been around since the early 1980s. Essentially a spreadsheet consists of multiple cells. A cell contains data in the form of numbers, alphanumeric text or formulas. These multiple cells make up a grid consisting of rows and columns. A formula can be used to define how the contents of that cell can be calculated from the contents of any other cell. One of the main uses of spreadsheets is in financial markets where real time share prices can be used to recalculate and - Databases
Databases
What is a database? Students must carry out at least one exercise using a database in order to fulfill Aim 7 (develop and apply the students’ information and communication technology skills in the study of science) but it does not have to be assessed. Scientists for a long time have used written lists of data – perhaps one of the best sources was the hardback book: CRC Press Handbook of Physics and Chemistry. However now a database specifically refers to computerised software containers that enable users to retrieve, add, update or remove - Computer modelling
Computer modelling
Simulations During your practical programme you need to explain the importance (and limitations) of using computer models to simulate experiments and each student should have personal experience of using computer modelling. There are many sites on the web where you can download good examples although you need to be careful about the level. Some universities have very sophisticated models which are probably too complex for our students. At the opposite end of the spectrum there are many very trivial examples which might be suitable for younger students but are unlikely
- Data logging
- Group 4 Project
Group 4 Project
Background The IB Group 4 Project is probably unique in forming part of any Chemistry programme for 16-19 education. It came into being after the major revision of the syllabus in 1996 (first examinations 1998). Chemistry teachers seem to either love it or hate it. In the consultation paper circulated to teachers before the 2001 review (for first examination in 2003) 50% of the teachers wanted to keep it and 50% wanted to scrap it. In the event the time which should be spent on it was changed so that- Practicalities
Practicalities
When to do the Group 4 Project It is worth considering that although it does have to be assessed it is only for a very small number of marks and the students do not need a lot of knowledge of subject content before they attempt it. It also seems better to ‘get it out of the way’ before the heavy demands of the Extended Essays and TOK essays etc. fall on the students. For this reason almost all schools carry out the Group 4 Project in the first year. For - Assessment
Assessment
Assessing Personal skills The Group 4 Project is the one and only time that Personal skills are assessed. This does actually create one small problem. What happens if a student is absent when the Group 4 Project is being done? They cannot do it on their own when they return to school and other students will not want to repeat it. There does not seem to be an easy solution to this. If others are absent too then a re-run can be arranged but what if they are the only
- Practicalities
- Assessment
Assessment
The five Assessment Criteria The IB practical programme has one very great strength - teachers are completely free to devise their own practical programme. There is absolutely no requirement for students to perform any one specific practical or experiment. All that is required is that during the 40 hours (SL) or 60 Hours (HL) programme sufficient investigations are undertaken for five different criteria to be assessed. Design (D) Data collection and processing (DCP) Conclusion and evaluation (CE) Manipulative skills (MS) Personal skills (PS)- Significant figures
Significant figures
The correct use and importance of significant figures Students often loose marks in their practical work (and in their written exams and Extended Essays) through the incorrect use of significant figures. Sometimes it is simply due to carelessness. A classic case is giving an answer from an experiment involving a titration to three significant figures when the burette readings have correctly been given to four significant figures (such as 25.35 cm-3) but the concentration of the acid or base used in the burette has only been given as 0.1 mol - Error & uncertainty
Error & uncertainty
The importance of error and uncertainty As part of their assessment students do need to take errors and uncertainties into account. They should know (or be able to estimate) the uncertainty associated with each piece of apparatus they use and have an awareness of which might significantly affect the result of their experiment. They should also have an awareness of uncertainties due to assumptions made. For example: Have all the chemicals reacted? How pure are the chemicals? Are there other products formed or side-reactions taking place, etc.? Students are expected to - Design
Design
The facts The IB places Design as the first of the criteria to be assessed. There is some logic in this as an experiment has to be designed (by someone) before meaningful data can be collected, processed, and evaluated. I've followed this practice but in reality almost all teachers will assess several 'recipe-type' experiments for Data collection and processing (DCP) and Conclusion and evaluation (CE) before setting and assessing Design practicals. The Design criterion tests whether the student can define a relevant problem and identify and select the variables then- Aspect 1 (D)
Aspect 1 (D)
Basic information To get ‘complete' for this aspect the student has to “Formulate a focused problem (or research question) and identify the variables.” Essentially this aspect can be broken down into two separate areas - the research question and the variables. Your task is to give a suitable area for investigation where each student in the class can potentially come up with a different focused problem or research question. What this means is that the area of investigation is only suitable if there is a large number of variables. Before - Aspect 2 (D)
Aspect 2 (D)
Basic information To get ‘complete' for this aspect the student has to “Design a method for the effective control of the variables” Many students find this aspect challenging and fail to gain ‘complete’ usually because they do not clearly state how all the variables are to be controlled. This is reflected in the comments in the May 2009 Chief Examiner’s Report, “This was the most challenging of the Design Aspects and many candidates failed to identify any procedural methods to control or at least monitor the control variables that they - Aspect 3 (D)
Aspect 3 (D)
Basic information To get ‘complete' for this aspect the student has to “Develop a method that allows for the collection of sufficient relevant data”. Advice to give to students The two important words in this aspect are ‘sufficient’ and relevant. The subject guide gives considerable help here. Clearly the definition of ‘sufficient relevant data’ will depend on the context. The method given should provide enough information to be collected so that the aim of the research question can be scientifically addressed and evaluated. For example, if a trend line
- Aspect 1 (D)
- Data collection & processing
Data collection & processing
The facts This criterion tests whether the student can record and process raw data and present the processed data. Raw data includes both quantitative measurements (including units and uncertainties where appropriate) and qualitative observations. Processing involves manipulating the raw data mathematically by for example transforming it into a form suitable for graphing and taking a gradient. Presenting the processed data includes propagating the uncertainties as well as choosing a suitable presentation format. Data collection and presentation Level (marks) Aspect 1 Recording raw data Aspect 2 Processing raw data- Aspect 1 (DCP)
Aspect 1 (DCP)
Basic information To get ‘complete' for this aspect the student has to “Record appropriate quantitative and associated qualitative raw data, including units and uncertainties where relevant.” Your task is to set a suitable practical where the student will have sufficient data (and uncertainties to record). This in itself is not a problem but you also need to bear in mind the other two aspects. On the main Data collection and processing page three specific practicals are suggested. The actual way in which all the processed data is presented is assessed - Aspect 2 (DCP)
Aspect 2 (DCP)
Basic information To gain 'complete' for Aspect 2 students are required to “Process the quantitative raw data correctly”. This sound simple enough but the Subject Guide goes on to explain what is meant by processing. Processing in this context involves combining and manipulating raw data (by, for example, adding, subtracting, squaring or dividing) to determine the value of a physical quantity and taking the average of several measurements and transforming data into a form suitable for graphical representation. If the data is already in a form suitable for a graph - Aspect 3 (DCP)
Aspect 3 (DCP)
Basic information To receive ‘complete’ for this aspect the student has to “Present processed data appropriately and where relevant, include errors and uncertainties". Essentially the student needs to meet two separate requirements for this aspect. Presentation of processed data The presentation format should be suitable to the requirements. In all cases where a graph is plotted students should choose a sensible scale for the axes, label both axes with the quantity and units, plot the data accurately and also give the graph a clear and unambiguous title. Calculations and tables
- Aspect 1 (DCP)
- Conclusion & evaluation
Conclusion & evaluation
The facts This criterion tests whether students can properly deduce a conclusion from their processed data and can look critical at the experimental method to determine where the weaknesses and limitations lie. It also tests whether they can then make sensible and realistic suggestions to improve the method to minimise or overcome these limitations and weaknesses. Conclusion and evaluation Level (marks) Aspect 1 Concluding Aspect 2 Evaluating procedure(s) Aspect 3 Improving the investigation Complete (2) States a conclusion, with justification, based on a reasonable interpretation of the data. Evaluates- Aspect 1 (CE)
Aspect 1 (CE)
Basic information To achieve 'complete' for this aspect students must "State a conclusion, with justification, based on a reasonable interpretation of the data". Students sometimes struggle with a conclusion. It is worth quoting form the May 2009 Chief Examiner's Report, "Although most candidates could achieve some credit, this proved a demanding aspect and few candidates successfully placed numerical results in the context of a literature value and then identified whether the difference required the invocation of system error." In one sense students have already given some sort of conclusion when - Aspect 2 (CE)
Aspect 2 (CE)
Basic information The requirements needed to achieve ‘complete’ for this aspect are very simply stated as “Evaluate weaknesses and limitations". There is a tendency for many students to look at the quality of the data by simply stating the uncertainties associated with each piece of apparatus whilst ignoring any underlying weaknesses or assumptions made in the design and method of the investigation. Advice to give to students What you will need to do is teach your students to not only identify the weaknesses but also to appreciate how significant - Aspect 3 (CE)
Aspect 3 (CE)
Basic information To gain ‘complete’ for this aspect students need to “Suggest realistic improvements in respect of identified weaknesses and limitations”. Clearly to be able to do this successfully they do need to have identified the major weaknesses in Aspect 2 and also realised the significance of each weakness. It is worth noting the instructions given to moderators listed in the May 2009 Chief Examiner’s Report. “It is important that the suggested modifications be realistic and should relate in the main to the weaknesses. Be sensible. If the candidate has
- Aspect 1 (CE)
- Manipulative skills
Manipulative skills
Facts The criterion Manipulative Skills (MS) is different to the first three criteria (D, DCP and CE) in several ways: It is assessed summatively over the whole two year course. It is only assessed once (so is worth a maximum of six marks) No evidence is required for moderation (this is also true for Personal Skills (PS)) The assessment should be based on a wide range of different manipulative skills. This criterion recognises that students may start the course with very different experience and knowledge of practicals skills. - Form 4/PSOW
Form 4/PSOW
Group 4 practical scheme of work (4/PSOW) Before you enter your IA marks in March/April you will need to complete a form 4/PSOW detailing the practical scheme of work and any marks awarded for each student at both levels. You can obtain a blank 4/PSOW form from your IB co-ordinator as they are contained in the IB Information handbook (make sure you get one for the correct year just in case there have been any changes) or, if you prefer, you can make up your own form using Excel. This - Moderation
Moderation
How the sample is chosen At the end of March you will need to enter all your Internal Assessment marks (out of 48) for each student along with their predicted grade. Make sure that any internal standardization has taken place before you finalize your marks. The exact date you enter the marks is not too important provided you do it before 10 April (May session) or 10 October (November session) but you will need to leave enough time to get all your samples ready and then sent to your IA
- Significant figures
- Marked practicals
Marked practicals
Rationale It can be very helpful to see how practicals are marked in order to get some idea of the standard applied. In some ways it does not really matter if you are slightly too lenient or slightly too harsh as long as you are consistent as that is the purpose of moderation. It does help to have practice though. The problem with exercises is that they are not the real thing. Firstly they are not your own students' work and secondly you tend to be more particular on an- Using Hess's Law
Using Hess's Law
Background This is a genuine write-up by one of my students. She was in fact a Higher Level student but could equally well have been following the Standard Level course as the practical is suitable for core chemistry. She was told that Data collection and processing (DCP) and Conclusion and Evaluation (CE) would be assessed for the second practical on Enthalpy Changes. The theory of Hess's Law had been covered in class and she had also written up the first practical on Enthalpy Changes (ΔH for the reaction between copper(II) - Solubility of calcium hydroxide
Solubility of calcium hydroxide
To determine the solubility of Ca(OH)2 by titration Background This experiment was given to Standard Level students. As it is a relatively simple experiment to perform, the instruction were given verbally. They were told to dissolve as much solid calcium hydroxide as they could in about 100 cm3 of water with stirring then leave the solution standing overnight ensuring that it contained some undissolved calcium hydroxide. Next day they were told to filter the solution and titrate 10.00 cm3 aliquots of the solution with standard 0.05 mol dm-3 hydrochloric acid - Aspect of rate of reaction
Aspect of rate of reaction
A Design experiment on rate of reaction Background This is a genuine account of a Design experiment. The Standard Level student had studied rates of reaction in class and had previously done a non-assessed experiment with sodium thiosulfate and hydrochloric acid to look at factors affecting the rate of a reaction. The only instructions the students in the class were given beforehand was to design their own an experiment to investigate one aspect of the rate of a chemical reaction. This student chose a relatively straightforward reaction and aspect to
- Using Hess's Law
- A new laboratory?
A new laboratory?
New laboratories Building or refurbishing a new laboratory If you are working in a brand new school or one which is being refurbished you may be involved with or consulted over the design and installation of a new chemistry laboratory. Different countries will have their own legal requirements and different schools will be working to different budgets. Among things to consider are: the maximum number of students to cater for the supply and positioning of services such as water, electricity and gas heights and sizes of workbenches adequate lighting fume cupboards and general
To see a brief extract of a page in this section hover over the relevant heading. Red borders indicate free pages. The blog is also free. To access other pages you must subscribe.
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| A new laboratory? | Analysis of aspirin tablets |
| Assessment | Aspect 1 (DCP) |
| Design practicals | CaCO3 in egg shells |
| Introduction | Determining Ea for a reaction |
Summary
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Selected Pages
Le Chatelier's principle - free
Using a colour change is one of the best ways to demonstrate chemical equilibrium and Le Chatelier's principle. In fact students will already have met a simple example when they used an... more»
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Assessment statement 6.1 contains the definition of rate of reaction and asks students to be able to suggest practical ways in which the rate of a reaction can be determined. There are... more»
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This is one of the classic experiments and you can find many examples giving details of it online. I think it is worth doing as it is tried and tested and gives... more»
CaCO3 in egg shells - free
This practical can be adapted to determine the amount of calcium carbonate in a variety of different substances ranging from eggs shells to the shells of sea creatures, such as crabs, or... more»
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This is a genuine write-up by one of my students. She was in fact a Higher Level student but could equally well have been following the Standard Level course as the practical... more»
Analysis of aspirin tablets - free
It is an interesting fact that if you buy generic aspirin tablets they are very much cheaper than packets of branded aspirin. The analysis shows that they all usually contain the same... more»
- ► Introduction
- ►▼ Devising a programme
- ►▼ Individual practicals
- ►▼ Practicals for SL & HL
- ► Common chemical reactions
- ► Formula of magnesium oxide
- ► Acid-base titrations
- ► A green acid-base practical
- ► Analysis of aspirin tablets
- ► CaCO3 in egg shells
- ► Period 3
- ► Chlorine in swimming pools
- ► Boiling points of mixtures
- ► Enthalpy changes
- ► Reaction rates
- ► Rate-dependent factors
- ► Le Chatelier's principle
- ► Group 7
- ► Redox titration with KMnO4
- ► Electrolytic cells
- ► Electrochemical cells
- ► Titrations with a pH meter
- ► Organic functional groups
- ► Hydrolysis of halogenoalkanes
- ►▼ Practicals for HL only
- ►▼ Practicals for options
- ► Other ideas
- ►▼ Practicals for SL & HL
- ►▼ Design practicals
- ►▼ ICT
- ►▼ Group 4 Project
- ►▼ Assessment
- ►▼ Marked practicals
- ► A new laboratory?
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“One is almost tempted to say….at last I can almost see a bond. But that will never be, for a bond does not really exist at all: it is a most convenient fiction which, as we have seen, is convenient both to experimental and theoretical chemists.”
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